1. Field of Invention
The present invention relates to a Chinese abacus adder. More particularly, the present invention relates to a Chinese abacus adder that has a multiple radix.
2. Description of Related Art
An Adder is a very important operational unit in an Arithmetic Logic Unit. The most common Ripple Carry Adders and Carry Look-ahead Adders are used in many related fields and applications.
The Chinese abacus is one of the most widely used arithmetic devices used historically in Eastern society. However, the theory of the Chinese abacus was only applied to the abacus adder circuit of the adder in 1998.
Franco Maloberti and Chen Gang proposed a circuit structure that included four parts: (1) a B/T (binary to thermometric) circuit, (2) an up shifter (US), (3) a T/A (thermometric to abacus) circuit and (4) an A/B (abacus to binary) circuit. Each part can only do a 2-bit adding operation of A plus B. If it is applied to multiple-bit operational circuits, it is necessary to occupy a large circuit area and the number of elements are also increased. The power consumption of all the circuits and the operational speed are also influenced.
In addition, designing a known high-bit fast adder such as the behavior mode of a carry look-ahead adder is described by the following equations (a), (b) and (c):Gi=AiBi  (a)Pi=(Ai⊕Bi)  (b)Ci+1=Gi+PiCi  (c)
Most of operational units are 32-bit or 64-bit nowadays so the aforementioned circuit structures are unsuitable for current ALU. Embodiments according to the present invention achieve the circuit functions described by equations (a), (b) and (c), and combine with multiple abacus adders to form a high-bit fast abacus adder.